VIPJAVA/02_JavaWeb/day10_mybatis/target/classes/com/lc/mapper/UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.lc.mapper.UserMapper">

    <!--
        动态sql if 标签
        test=""  OGNL 表达式

        select * from t_user where and password = ?  sql 问题


     -->
    <select id="getUserByNameAndPass" resultType="user" >
        select * from t_user
        <where>
            <if test="name != null and name != ''  ">
                username = #{name}
            </if>
            <if test="pass != null and pass != ''  ">
                and password = #{pass}
            </if>
        </where>
    </select>

    <!--
        set 解决 逗号问题
     -->
    <update id="updateUserById">
        UPDATE `db2`.`t_user`
        <set>
            <if test=" username != null and username != '' ">
                `username` = #{username},
            </if>
            <if test=" password != null and password != '' ">
                `password` = #{password},
            </if>
            <if test=" gender != null and gender != '' ">
                `gender` = #{gender},
            </if>
            <if test=" address != null and address != '' ">
                `address` = #{address},
            </if>
            <if test=" deptId != null and deptId != '' ">
                `dept_id` = #{deptId}
            </if>
        </set>
        <where>
            <if test="id != null and id !='' ">
                `id` = #{id} ;
            </if>
        </where>
    </update>


    <!--
        trim
            属性
            prefix  前缀
            prefixOverrides  覆盖前缀
            suffix  后缀
            suffixOverrides 覆盖后缀
     -->
    <select id="getUserByNameAndPassTrim" resultType="user" >
        select * from t_user
        <trim  prefix="where" prefixOverrides="and" >
            <if test="name != null and name != ''  ">
                and username = #{name}
            </if>
            <if test="pass != null and pass != ''  ">
                and password = #{pass}
            </if>
        </trim>
    </select>

    <!--
        foreach

        collection 集合
        open 开始符号
        close 结尾
        separator 中间符号
        index 索引
        item 每一项
     -->
    <select id="getUserByIds" resultType="user" >
        select 
            <include refid="userSql"></include>    
        from t_user where id in
        <foreach collection="ids" open="(" item="id" separator="," close=")">
            #{id}
        </foreach>
    </select>

    <!--
        sql 片段
    -->
    <sql id="userSql">
        username , password , gender , address , dept_id
    </sql>

</mapper>